Along with the increasingly small size and greater number of functions of electronic devices, the circuit boards which are used for electronic devices are also being required to be made higher in density. To make circuit boards higher in density, the general practice is to make the circuit boards multilayered. Such multilayer circuit boards, for example, are comprised of an inner layer board in which a conductive circuit layer is formed on the outermost surface, an electrical insulating layer laminated on its surface, and a conductive circuit layer which is further formed on the electrical insulating layer. If desired, several electrical insulating layers and conductive circuit layers may be laminated.
In such a multilayer circuit board, to extend the lifetime of the circuit board and secure the reliability, the bondability between the electrical insulating layer and the conductive circuit layer which is formed on it is important. As art for improving the bondability, for example, Patent Document 1 discloses a method of production of a multilayer circuit board on which at least an insulating resin layer and a conductor interconnect layer are formed comprising forming a foundation layer which contains a coordination polymer complex between the insulating resin layer and conductor interconnect layer. Further, Patent Document 2 discloses a method of production of a multilayer circuit board comprising forming on an inner layer board which has an outermost layer of a conductive circuit layer 1 an uncured or semicured resin layer by using a curable composition which contains an insulating polymer and a curing agent (step A), then bringing a compound which has a structure which can coordinate with a metal into contact with the surface of that resin layer (step B), next curing that shaped member to form an electrical insulating layer “b” (step C), forming a metal thin film layer on the surface of this electrical insulating layer “b” (step D), then forming a conductive circuit layer 2 including that metal thin film layer (step E).